Chapter 8 Parallel System
Fig. 8-4 Series backup mode
Note
The default value of alternative operation time is 168 hours and the range is
8.1.3 Operation modes
The parallel operation system also has operation modes such as normal mode, battery mode, bypass mode and maintenance bypass mode. All the UPS units inside the parallel operation system should operate in harmony. For example if one UPS is in inverter mode, the bypass of other units should be shut down.
Normal mode: The load is powered by the inverters of all the UPS units inside the system. If the bypass frequency is in the synchronous range, the inverter will be synchronous with the bypass. Otherwise, the system will operate at nominal frequency.
Battery mode: The batteries of the system powers the load through inverters of all the UPS units. The system operates at nominal frequency.
Bypass mode: The condition to transfer to bypass mode is same with that of single module UPS system. The bypasses of all the UPS units power the load.
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